Discover the millions of microorganisms in soil. Material processes - Classifying materials - Soil Learning Points Soil is a mixture of rock particles, organic matter, air and water. Soil is formed over many years when rock is weathered into small particles. A Twig Curriculum Film. Delivering key learning points. Get straight to the facts in just three minutes – directly linked to core learning, Twig's curriculum films will fit neatly into your lesson plans.